A recent mobile phone has become thinner and thinner. According to this trend, a substrate used therein, of course, also has become thinner. However, as the mobile phone becomes thin, a curvature of a folded substrate becomes too much such that the substrate may be damaged. Here, the curvature generally means being folded in a bow-shaped manner and, in particular, it signifies an evenly-curved curvature of a bend (for example, the bend having the radius of the curvature continuously and smoothly changing) and the above-mentioned substrate and the like may be used under such a curvature condition. Hence, the test is conducted before the actual use, but it is an issue if the substrate works in a normal way or not especially when the substrate is folded in the bow-shaped manner. It has been conventionally judged whether the substrate is appropriate or not by bending the substrate in the bow-shaped manner by hand. However, it is not efficient to conduct such a test by hand for each substrate with respect to each different curvature radius of the curvature and each different arc length (length of a bent portion).
Although the folding itself can be conducted by a machine if it is wished to use the machine, the folding test may not be able to be conducted depending on the way of conduction.
Unexamined laid-open Japanese patent application No. 2013-057538 discloses a device which conducts the folding by the machine. However, the device shown in the reference is to simply bend a specimen to be examined, but not to bend the specimen to have the evenly-curved curvature of the bend, although the device relates to bending of a planar body. And the device is not a test device to test the specimen by changing the curvature radius of the bend.